Clock synchronization deals with the issue that internal clocks of several computers may differ. Even when initially set to the same time, internal clocks will differ after some time due to clock drift, which is caused by each clock counting time at a slightly different rate.
In a distributed computer system, in which multiple autonomous computers communicate via a computer network, clock synchronization is implemented by establishing a “global” time (i.e., a standard time among all computers in the network). After establishing the global time (also referred to herein as a “reference clock time”), the global time needs to be accurately maintained across all nodes of the computer network.